| Hydroxy-terminated poly(2,2-substituted-1,3-propylene oxide) polyoxetane telechelics and co-telechelics (Tg's, -33 to -39°C; MW ∼3-5 x 103 g/mole) bearing semifluorinated soft blocks (-CH2OCH2(CF2) nCF3) and functional bromomethyl pendant groups were synthesized and incorporated in polyurethanes with isophorone diisocyanate and 1,4-butanediol as the hard block. Characterization was carried out utilizing 1H NMR spectroscopy, both standard and temperature-modulated differential scanning calorimetry (MDCS), and gel permeation chromatography (GPC).;Polyurethane (PU) surface properties were evaluated using tapping-mode atomic force microscopy (TM-AFM) and dynamic contact angle (DCA) analysis. The polyurethanes containing P(3FOx-BrOx) have higher thetaadv and lower thetarec than the homo-telechelic PUs. For IPDI-BD(40)/P(3FOx:BrOx-1:1), theta adv (116°) is higher and thetarec (32°) is lower (Deltatheta, 84°) than parent homo-telechelic polyurethanes. FOx-BrOx dyad content and a reversible H-bonding mechanism was proposed to explain these phenomena. These polyurethanes were employed as polymeric surface modifiers (PSMs) for surface modification of a conventional base polyurethane (0.5-2.0 wt %). The functional groups (bromomethyl) were aggregated at the air-polymer interface by employing high surface affinity of semifluorinated side chains. The surface enrichment of PSM was verified by TM-AFM, X-ray photoelectron spectroscopy (XPS), and DCA analysis.;The bromomethyl groups were then substituted with 5,5-dimethylhydantoin moieties. The bulk characterization of resulting polyurethanes utilized 1H NMR, both standard and temperature modulated DSC, and GPC. The DCA analysis displayed an unexpected wetting behavior: the dry polyurethane surfaces become more hydrophobic as it became wet. The term "contraphilic" was suggested for this reversible change, opposite expected amphiphilic behavior. Amide inter/intra molecular hydrogen bonding was proposed for the hydrophilic (dry) state when the surface wetted an amide-water hydrogen bond formed releasing the semifluorinated groups giving the hydrophobic state.;Initially, 5,5-dimethylhydantoin substituted polyurethanes were employed as biocidal PSMs for a conventional polyurethane coating. The PSM modified polyurethane was activated by converting near-surface amide groups to chloramide with 3 wt hypochlorite. Biocidal activity against both Gram-positive ( Staphylococcus aureus) and Gram-negative (Pseudomonas aeruginosa , and Escherichia coli) bacteria was demonstrated by using a modified version of American Association of Textile Chemists and Colorists (AATCC-100) test. By changing the PSM concentration, it was found that only 1.6 wt % PSM (0.66 wt % biocide, 5,5-dimethylhydantoin) in a conventional polyurethane affected complete kill of Pseudomonas aeruginosa in 15 minutes, by using this biocidal testing protocol. |
